Conventional examples of X-ray image taking means in the field of medical diagnosis include: an image detecting apparatus which operates in a S/F (Screen/Film) scheme using an intensifying screen and a film; an image detecting apparatus which operates in a CR (Computed Radiography) scheme in which a latent image recorded on an imaging plate is read by laser scanning; and an image detecting apparatus which operates in. I.I.-TV (Image Intensifier TV) with a combination use of a photomultiplier and a CCD. However, in recent years, flat-panel digital radiation detecting apparatuses have been increasingly developed and commercialized as new image detecting apparatuses, which are alternatives to the above image detecting apparatuses. The flat-panel radiation detecting apparatuses have, as a key device, a flat sensor panel including (a) a thin-film transistor (TFT) array arranged in two dimension and (b) a conversion film (element) which converts X-rays into electrical signals. The flat-panel radiation detecting apparatuses have various advantages as compared with the conventional X-ray image detecting apparatuses. Specifically, the flat-panel radiation detecting apparatuses realize a filmless structure and facilitates image quality improvement and diagnosis support with digital image processing, electronic filing, and networking, as compared with the conventional image detecting apparatuses which operate in the S/F scheme. Further, the flat-panel radiation detecting apparatuses are capable of converting an image detection result into image signals in an instant, as compared with the conventional image detecting apparatuses which operate in the CR scheme. Still further, the flat-panel radiation detecting apparatuses realize extensive sliming down and provides large X-ray images with high resolution, as compared with the conventional image detecting apparatuses which operate in the I.I.-TV scheme.
The flat-panel radiation detecting apparatuses are broadly classified into apparatuses which operate in a “indirect conversion scheme” and apparatuses which operate in a “direct conversion scheme” in terms of difference in X-ray detection principle. The “indirect conversion scheme” is a scheme in which X-ray information is converted into light by means of fluorescent material (Scintillator), and the light is then converted into electrical signals image to obtain image information.
Meanwhile, the “direct conversion scheme” is a scheme in which X-ray information is directly converted into electrical signals by means of an X-ray conversion film (X-ray photoconductor) to obtain image information. When the “indirect conversion scheme” and “the direct conversion scheme” are compared, the “direct conversion scheme”, which is not affected by light scattering because it does not include the process for converting X-ray information into light, is able to provide image information with high resolution. Thus, it can be said that the “direct conversion scheme” is suitable for radiation detecting apparatuses which are demanded for high resolution.
FIG. 13 is a plan view schematically illustrating the structure of a sensor panel (including peripheral circuit substrates 113) adopted in the conventional radiation detecting apparatus 100 in the “direct conversion scheme”. FIG. 14 is a cross-sectional view of the radiation detecting apparatus 100, taken from a F-F′ line of FIG. 13. In FIG. 14, the active matrix substrate (thin-film transistor array) 102 has a plurality of pixel electrodes 101, serving as electric charge collectors, on its surface. On the active matrix substrate 102, a conversion layer 103 (semiconductor film made of Selenium or the like) and an upper electrode 104 are provided in sequence. The conversion layer 103 converts X-rays into electric charges. On the active matrix substrate 102, latticed electrical wiring (not shown) in an XY matrix is formed. For each segment of the latticed electrical wiring, a thin-film transistor (TFT; not shown) and an electric charge storage capacitance (not shown) are formed, connected to the pixel electrode 101.
Next, the following description will discuss a mold structure 105, which is formed so as to cover the conversion layer 103 and the upper electrode 104. In FIGS. 13 and 14, a counter substrate 106 is provided so as to protect the conversion layer 103 and the upper electrode 104 in sequence on the active matrix substrate 102. The counter substrate 106 is provided so as to form a gap between the counter substrate 106 and the upper electrode 104 by means of a sealing material (mold material) 107, which is provided around the perimeter of the counter substrate 106. The gap is filled with a mold resin (mold structure 105). The mold structure 105 provided in this manner makes it possible to protect the conversion layer 103 and the upper electrode 104 from moisture (water), dust, and the like, and makes it possible to prevent electric charge caused by a high voltage applied to the upper electrode 104. Patent Document 1 (Japanese Unexamined Patent Publication No. 148475/2001 (Tokukai 2001-148475); published on May 29, 2001) discloses a two-dimensional image detector including a mold structure.
Incidentally, as discussed previously, the flat-panel radiation detecting apparatuses in the “direct conversion scheme” are suitable for applications that require high resolution. As such, expectations have been placed on their applications to mammography.
In mammography (X-ray photography only for breasts), a subject (i.e. breast) must be brought intimate contact with a photographing side of a photographing apparatus to photograph the subject.
Mammography with a general photographing apparatus had the problem that a part of the subject lies off the edge of the image. This was caused by a distance between an effective photographing area and the edge of the photographing apparatus.
Now, the following description will discuss mammography using a general photographing apparatus with reference to FIG. 15.
FIG. 15 is a cross-sectional view schematically illustrating a relation a general photographing apparatus 110 (e.g. radiation detecting apparatus 100 of FIG. 13) and a subject 120. Examples of the subject 120 include breasts, objects protruded through a base plane H, and objects that cannot be physically separated from the base plane H. FIG. 15 assumes that the subject 120 is a round object that cannot be physically separated from the base plane H. Note that the base plane H is inviolable, so that it is impossible for the photographing apparatus 110 to enter into the base plane H.
As illustrated in FIG. 15, an X-ray image of the whole of the subject 120 cannot be obtained in the photographing apparatus 110 because part of the subject lies off an image detection area A. The image detection area A corresponds to an area where pixel electrodes are arranged.
Radiation detecting apparatuses which can be used in mammography are disclosed in Patent Document 2 (Japanese Unexamined Patent Publication No. 314056/2002 (Tokukai 2002-314056); published on Oct. 25, 2002) and Patent Document 3 (Japanese Unexamined Patent Publication No. 17673/2003 (Tokukai 2003-17673); published on Jan. 17, 2003), for example. In the techniques disclosed in Patent Documents 2 and 3, at least one end of an outer region of a photographing apparatus (image detecting apparatus and irradiation image detecting apparatus), i.e. ends of the apparatus is arranged so as to be very close to an image detection area on a photographing side of the apparatus. In photographing the subject 120, for example, this arrangement does not cause the problem that a part of the subject is not photographed, and makes it possible to excellently carry out photographing. As such, such a photographing apparatus is suitable for mammography.
However, unlike techniques disclosed in Patent Documents 2 and 3 discussed above, a two-dimensional image detector having a structure as shown in FIGS. 13 and 14, disclosed in Patent Document 1, includes gate drivers (LSIs) 111 and signal reading amplifiers (LSIs) 112 in the whole of a non-detection area (area that is not capable of image detection, provided around the image detection area) of the active matrix substrate 102.
Even in a case where the gate drivers (LSIs) 111 and the signal reading amplifiers (LSIs) 112 are moved to another place to have an area where no LSIs are disposed at one portion of the non-detection area, the following problem arises.
That is, in a two-dimensional image detector disclosed in Patent Document 1, a sealing material (corresponding to sealing material 107 in FIG. 14), which is disposed so as to surround an X-ray conductive layer (corresponding to the conversion layer 103 in FIG. 14) is used in forming a mold structure. The sealing material serves to ensure a gap between an active matrix substrate and a counter substrate and to secure the active matrix substrate and the counter substrate by bonding. In such a case, contact or overlap between the sealing material and a part of the X-ray conductive layer is not preferable in view of securing of bonding between the sealing material and the active matrix substrate. In manufacturing, the sealing material is therefore disposed so as to be some distance from the X-ray conductive layer. As a result, to provide a mold structure, the X-ray conductive layer and the sealing material are inevitably apart from each other at a predetermined distance.
For this reason, even a two-dimensional image detector which brings the above beneficial effect with the adoption of a mold structure, is difficult to be applied to mammography.
The present invention has been attained in view of the above problems, and an object of the present invention is to provide a two-dimensional image detecting apparatus which includes a mold structure and is applicable to mammography. Additionally, an object of the present invention is to provide a method for manufacturing a two-dimensional image detecting apparatus, including a step of processing a two-dimensional image detecting apparatus having a mold structure formed therein so as to be applicable to mammography.